PCNA and hydrops fetalis: In the rostral HF, time spent in both outdoor areas (the stone yard and grassy range) was positively associated with expression of PCNA. This relationship may be attributable to the stimulatory effect of factors including environmental complexity and exercise on hippocampal proliferation, as such experiences have been observed to preferentially modulate AHN in the dorsal rodent HF (48, 50, 78).